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Blue Butterfly Pea flower tea is blue by default. Add citrus juice and it turns purple. What compound or compounds are responsible for this reaction to change in pH?

Wikipedia doesn't say, nor can I find any source on the internet that does.

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  • $\begingroup$ Many pH indicators (all, actually) do similar colour changes. en.wikipedia.org/wiki/Red_cabbage#pH_indicator is a well known example. What did you do during chemistry lessons in school? ;-) $\endgroup$
    – Karl
    Sep 30, 2017 at 23:44
  • $\begingroup$ @Karl - Yes. Which pH indicator(s) is in the tea? $\endgroup$ Oct 1, 2017 at 0:00
  • $\begingroup$ I don't know what's the blue stuff in Clitoria Ternatea. Some biologist might be able to find out. Is it important for you? The colour change surely comes from one of the typical reactions that occur in pH indicators. $\endgroup$
    – Karl
    Oct 1, 2017 at 0:07
  • $\begingroup$ @Karl. I'm simply curious. I hope that's a good enough reason to post the question. $\endgroup$ Oct 1, 2017 at 0:15

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OK, that was simple. This

https://www.google.de/search?q=Clitoria+Ternatea+blue+color

gave this

https://www.ncbi.nlm.nih.gov/pubmed/14568080

which lead me to this

https://en.wikipedia.org/wiki/Anthocyanidin

and I guess that's the culprit. I judge from that abstract linked above that the actual plant can contain a wide mixture of those anthocyanidines.

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  • $\begingroup$ I guess my internet research chops need work :-/ Thanks. $\endgroup$ Oct 1, 2017 at 0:53
  • $\begingroup$ Another interesting article that also mentions this class of compounds in the context of potential anti-inflammatory uses: pubs.acs.org/doi/abs/10.1021/… $\endgroup$
    – TrinitronX
    Sep 26, 2018 at 15:30
  • $\begingroup$ So it is the same group of chemicals as in red cabbage. Interestingly if you get red cabbage juice on eggs they go blue, so I guess that's the inverse reaction to lemon in blue pea. $\endgroup$
    – naught101
    Feb 21 at 2:35

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